Process for electrically coating with tin or allied metals.



UNITED sTATEs PATENT curios.

JAY C. BENEKER, OF WAUKEGAN, ILLINOIS, ASSIGNOR TO THE MEAKER 00., OFCHICAGO,

ILLINOIS, A CORPORATION OF ILLINOIS.

PROCESS FOR ELECTRICALLY COATING WITH TIN OR ALLIED METALS.

To all whom it may concern:

Be it known that I, JAY CARL BENEKER, a citizen of the United States,and a resident of the city of Waukegan, in the county of Lake and 'Stateof Illinois, have invented certain new and useful Improvements inProcesses for Electrically loating with Tin or Allied Metals, of whichthe following is a specification.

The use of a solution containing a salt of tin or allied metal such asantimony, platinum, gold or mercury or mixture of any. two (2) or moreof these when an allo is to be deposited that can form a so-cal edsulfosalt of an alkalineor alkaline earth metal.

The object of the invention is. to render the process more expeditious,considerably. cheaper, and to afford a homogeneous coating of uniformthickness and density. v In carrying out my invention I use a solutioncontaining an ous or an ic salt of tin or an allied metal capable offorming a so called sulfo-salt of an alkaline or alkaline earth metal,of a mixture of any two or more of such s'alts when an alloy is to bedeposited. An alkaline or an alkaline earth hydrate, preferably sodiumhydroxid and an alkaline thio sulfate such as sodium thio sulfate betterknown as hyposulfite, are used.

Vihile I do not limit this application to definite proportions, thesemay of course be varied and I recommend the following formula as givingsatisfactory results for tin coating: 25 parts sodium hydrate, partssodium thio sulfate, 10 parts crystallized stannous chlorid, 200 partwater. Preferably a solution is made of each, mixing the solution ofstannous chlorid and sodium hydrate. When the solution is complete addthe sodium thio sulfate. The solution. thus formed ma be used either hotor cold as an'electrolytic bath when plating, but I prefer to use ithot. T he reaction that takes (place is probably as follows:.lhe tinchlori combined with the sodium hydrate forming sodium stannite,

.znaonq sno,=Nao1+N ,s o,+H,o. i The thio sulfate then transforms thisstannite Specification of Letters Patent. Application filed June 27,1907. Serial No. 381,008.

to a sulfo-salt changing all or most of the Patented May 18, 1909.

stannous to'the stannic form. Probably the chief ingredient in the finalsolution is sodium thio-stannate Na -SnS This com pound in a high degreecan be electrolyzed without the tin separating in a spongy or tree form.

For tin coatings I employ thio sulfate for the purpose 'of transformingalkaline or alkaline earthstannites to alkaline or alkaline earth thiostannates, thus changing the valency from the ous to the ic form inwhich form only are the thio salts of tin known. These sulfo compoundsare also formed even when the valency is not changed as" in the casewhere mercuric or stannic salts are made the starting point.

With this solution'using any convenient anode. but preferably onecontaining the metal to be plated out, excellent deposits of tin-or anallied metal can be plated out without t 1e formation of a spongy ortreelike deposit, even when using high current densities. The solutioncontaining a goodly excess of caustic soda as in the above statedproportions-permits the tin or any suitable metallic anode used, to gointo solution quite readily even when using high current densities thusassuring a solution of fairly constant metallic content.

Of course my process is applicable to the plating of metals from theirores in which case a carbon or other insoluble anode is preferably used.A

I claim as my invention 1. An electrolytic solution for tin comprising asolution formed of solutions of ser ium hydrate and sodium thio sulfateto which a solution of stannous chlorid in proper .proportions is added.

2. An electrolytic plating solution of tin comprising approximatelyparts sodium hydrate, 15 sodium thio sulfate and 10 parts stannouschlorid and 200 parts of water.

In testimony whereof I have hereunto "subscribed my name in thepresenceoftwo subscribing witnesses.

.Witnesses:

K. E. HANNAH, J. W. ANGELL.

JAY o. BENEKE-R.

